From: Nick Piggin Date: Thu, 23 Jun 2005 07:08:52 +0000 (-0700) Subject: [PATCH] blk: no memory barrier X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=250dccc00805e755a6d80a73557034253da0831f;p=GitHub%2FLineageOS%2Fandroid_kernel_samsung_universal7580.git [PATCH] blk: no memory barrier This memory barrier is not needed because the waitqueue will only get waiters on it in the following situations: rq->count has exceeded the threshold - however all manipulations of ->count are performed under the runqueue lock, and so we will correctly pick up any waiter. Memory allocation for the request fails. In this case, there is no additional help provided by the memory barrier. We are guaranteed to eventually wake up waiters because the request allocation mempool guarantees that if the mem allocation for a request fails, there must be some requests in flight. They will wake up waiters when they are retired. Signed-off-by: Nick Piggin Cc: Jens Axboe Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c index c581f9138c4..265de858d4d 100644 --- a/drivers/block/ll_rw_blk.c +++ b/drivers/block/ll_rw_blk.c @@ -1842,7 +1842,6 @@ static void __freed_request(request_queue_t *q, int rw) clear_queue_congested(q, rw); if (rl->count[rw] + 1 <= q->nr_requests) { - smp_mb(); if (waitqueue_active(&rl->wait[rw])) wake_up(&rl->wait[rw]);